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Re: [pedantic-web] Re: The OWL Ontology URI

From: David Booth <david@dbooth.org>
Date: Wed, 12 May 2010 21:56:41 -0400
To: Dan Connolly <connolly@w3.org>
Cc: Pat Hayes <phayes@ihmc.us>, Jonathan Rees <jar@creativecommons.org>, AWWSW TF <public-awwsw@w3.org>
Message-ID: <1273715801.3264.25078.camel@dbooth-laptop>
On Wed, 2010-05-12 at 10:31 -0500, Dan Connolly wrote:
[ . . . ]
> "Other things, such as cars and dogs (and, if you've printed this document on physical
> sheets of paper, the artifact that you are holding in your hand), are resources too.
> They are not information resources."
> 
> so w:InformationResource is disjoint with cars, dogs, and pieces of paper.
> 
> That suggests fairly strongly that it's disjoint with people, but doesn't
> say so exactly. How about Graphs? Integers? I don't find any compelling
> argument based solely on ratified specs and/or decisions of the TAG.

It is pointless to make claims about what is or isn't disjoint with
w:InformationResource when we do not have either a formal definition --
a set of assertions -- of w:InformationResource or of "dog", "person",
etc.  If we make up RDF definitions of those terms *then* we can talk
about what is disjoint and what isn't.

Furthermore, as I've pointed out before, there is no architectural
*need* to define w:InformationResource as disjoint with something like
sumo:Person (from the SUMO upper ontology).  Ambiguity of resource
identity is inescapable -- we just have to accept that fact and learn to
deal with it -- so although the AWWW (correctly, in my view) admonishes
people to mint different URIs for different things, 
http://www.w3.org/TR/webarch/#URI-collision 
the choice of what to consider *different* (versus what to benignly
conflate) will always be an application-dependent judgement call that
seeks to balance immediate simplicity against support for other -- more
discerning -- uses of the URI(s).  A single URI for X may be perfectly
adequate and unambiguous for one application, while a different
application may need to distinguish between X1 and X2, which were
conflated by using a single URI for X.  

There is no significant benefit to the web architecture by trying to
insist that w:InformationResource must be distinct from some notion of
person.  The salient architectural advice was already given the AWWW
section on avoiding URI collisions:
http://www.w3.org/TR/webarch/#URI-collision
Given that advice, it is up to URI owners to decide where to draw the
line between simplicity and support for other uses of a URI.

(Incidentally, this does not mean that the notion of "information
resource" is useless: it is an important role in the web architecture.
An "information resource" is the kind of thing that can have
"representations".)

I know of no other reasonable and general way to define the identity of
a resource than by specifying a set of assertions that constrain it.
And of course, in the semantic web world, the natural way to do that is
with a set of RDF assertions.  Given that it would be (IMO) completely
nonsensical for different people to arbitrarily assume completely
different resource definitions for a given URI, the next logical
question is: how should the resource identity for a URI be determined?
Or another way to state this is: how should the resource identity for a
URI at least be *minimally* constrained, given that it will be further
constrained in different applications.  This leads to the notion of a
URI declaration.  
http://dbooth.org/2007/uri-decl/ 

One can think of a URI declaration as providing a set of constraints
that (minimally) limit the possible interpretations for that URI that
are permissible.  Of course, when a URI is used in a semantic web
application there will normally be *additional* assertions involving
that URI, and those will additionally constrain the potential
interpretations for that URI, just as illustrated in step 3a of figure
3:
http://dbooth.org/2009/denotation/ 

Thus, it is perfectly reasonable that one URI owner may mint a URI that
denotes something that is both an w:InformationResource and an RDF
graph, while another URI owner chooses to distinguish between them by
minting separate URIs.  Again, without a definition of the resource
identity for each URI (e.g., a URI declaration for each) there is no
basis for deciding whether they are disjoint or not.


-- 
David Booth, Ph.D.
Cleveland Clinic (contractor)

Opinions expressed herein are those of the author and do not necessarily
reflect those of Cleveland Clinic.
Received on Thursday, 13 May 2010 01:57:09 UTC

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